This invention relates generally to wireless networks and, in particular, to apparatus and methods for asymmetrical frequency spectrum utilization in a wireless network.
A standard allocation of frequency spectrum for use in a wireless network is illustrated in FIG. 1A. In this case, there is a first block of frequency spectrum, labelled A within FIG. 1A, which is used for up-link traffic while there is a second block of frequency spectrum, labelled B within FIG. 1A, which is used for down-link traffic. As defined herein, up-link traffic includes all communications from Mobile Terminals (MTS) to Base Transceiver Stations (BTSs) and down-link traffic includes all communications from the BTSs to the MTs. Further, as illustrated within FIG. 1A, there is typically a Frequency Gap (F.G.) between the up-link and down-link blocks of spectrum for separation purposes. One example of frequency spectrum allocation such as that illustrated in FIG. 1A is the implementation of the cellular communications band in North America. In this case, as labelled on FIG. 1A, up-link traffic is assigned the block of frequencies between 824 and 849 MHz and down-link traffic is assigned the block of frequencies between 869 and 894 MHz, thus maintaining a frequency separation of exactly 45 MHz between up-link and down-link channels.
With the use of the frequency spectrum allocation of FIG. 1A, companies purchase licenses for sub-blocks of spectrum within the A and B blocks, each sub-block comprising a plurality of Radio Frequency (RF) channels. For each company that purchases a license, their sub-block within the A block (the A sub-block) and their sub-block within the B block (the B sub-block) are located at relatively the same positions within their respective blocks. Thus, each of the Radio Frequency (RF) channels within the A sub-block has a corresponding RF channel within the B sub-block at a fixed frequency offset, the fixed 45 MHz frequency offset being the same for all of the RF channels within all of the sub-blocks. The fixed frequency offset allows for a single oscillator to be implemented within each MT for both the up-link and down-link communications. If there was a variable frequency offset, an oscillator would have to implemented for each possible offset, thus increasing costs and power consumption for the MT considerably.
Individual users of the wireless network must setup an account with one of the companies licensing sub-blocks of the frequency spectrum in order to have their MTs be assigned to RF channels within the up-link and down-link sub-blocks. Since not all users require bandwidth at all times, a system design is performed by each company that owns a frequency spectrum license to determine the number of users that it can assign to a particular set of RF channels without causing excessive amounts of blocked voice calls due to a lack of bandwidth. This system design balances revenue for the company versus caller satisfaction.
Companies holding cellular licenses may also hold licenses within the Personal Communications System (PCS) band located between 1850 and 1990 MHz (1850 to 1910 MHz for up-link communications, 1930 to 1990 MHz for down-link communications and 1910 to 1930 MHz for a guard band). In this case, users could purchase a uni-band MT that allows access to one of the two bands or a dual-band MT that allows access to both of the bands available from the particular company, the dual-band MT requiring two oscillators and two sets of tuned bandpass filters. FIG. 1B illustrates the situation in which there is a plurality of frequency bands available for use by the MTs, particularly the cellular band and the PCS band. In this case, there are the A and B blocks as described above with reference to FIG. 1A along with an additional frequency band comprising an up-link block labelled X and a down-link block labelled Y.
With the use of the frequency spectrum allocation as illustrated in any one of FIGS. 1A and 1B, there is a symmetrical allocation of frequency bandwidth for the up-link and down-link communications. This works well for voice communications that generally are full-duplex and symmetrical.
Unfortunately, data communications do not generally operate symmetrically. With numerous data communication applications, there is considerably more down-link data traffic than up-link traffic. For instance, a single short request from a MT connected to the Internet could result in the downloading of a considerable amount of data information. When compared to a typical voice session which might require 10 kbps within both the up-link and down-link blocks, a data session might typically require only 1 kbps in the up-link block and 100 kbps in the down-link block for efficient communications.
The result of this asymmetrical use of the up-link and down-link blocks is that the resources of the down-link block are being consumed much quicker than the resources of the up-link block. Thus, considerable bandwidth will be wasted within the up-link block, or the amount of bandwidth allocated to each user for down-link communications will be significantly limited, likely causing dissatisfaction with users.
Therefore, a new allocation method of frequency spectrum is required that complements the asymmetrical frequency usage caused by data communications. This new system will preferably allow for fixed offsets to be maintained between the paired up-link and down-link traffic, thus allowing for relatively simple and cheap MT implementations, while also allowing for additional bandwidth to be assessable for bandwidth hungry down-link communications.
The present invention is directed to apparatus and methods for implementing asymmetrical wireless communications without significant wastage of bandwidth within the up-link block of frequency spectrum. In embodiments of the present invention, the frequency spectrum is divided such that a single up-link block is paired with a plurality of corresponding down-link blocks of similar bandwidth size and respective fixed frequency offsets. In wireless networks of the present invention, MTs that utilize different down-link blocks share a common up-link block so that, in ideal statistical situations, the up-link block statistically runs out of bandwidth at approximately the same time as the combination of the down-link blocks.
The present invention, according to a first broad aspect, is a Base Transceiver Station (BTS) arranged to be implemented within a wireless network. The BTS includes one or more antennas; at least one receive apparatus coupled to the one or more antennas and first and second transmit apparatus each coupled to the one or more antennas. The receive apparatus operates to receive up-link signals from a plurality of mobile terminals within the wireless network via a channel within a first frequency block. The first transmit apparatus operates to transmit down-link signals to a first set of the plurality of mobile terminals via a channel within a second frequency block. The second transmit apparatus operates to transmit down-link signals to a second set of the plurality of mobile terminals via a channel within a third frequency block.
In preferred embodiments, the channels within the first and second frequency blocks have a first predetermined frequency offset and the channels within the first and third frequency blocks have a second predetermined frequency offset In one embodiment, this first predetermined frequency offset is set by the relative frequency tuning between first and second narrow-band BPFs within the receive and first transmit apparatus respectively while the second predetermined frequency offset is set by the relative frequency tuning between first and third narrow-band BPFs within the receive and second transmit apparatus respectively.
In another embodiment, the first predetermined frequency offset is set by a relative frequency difference between first and second reference oscillation signals input to the receive and first transmit apparatus respectively while the second predetermined frequency offset is set by a relative frequency difference between first and third reference oscillation signals input to the receive and second transmit apparatus respectively.
According to a second broad aspect, the present invention is a wireless network including a plurality of mobile stations and a Base Station Transceiver (BTS). The BTS operates to: receive up-link signals from each of the mobile terminals via a channel within a first frequency block, transmit down-link signals to a first set of the plurality of mobile terminals via a channel within a second frequency block and transmit down-link signals to a second set of the plurality of mobile terminals via a channel within a third frequency block
According to a third broad aspect, the present invention is a method for utilizing frequency spectrum within a wireless network. First, the method includes receiving up-link signals from each of a plurality of mobile terminals via a channel within a first frequency block. Next, the method includes transmitting down-link signals to a first set of the plurality of mobile terminals via a channel within a second frequency block and transmitting down-link signals to a second set of the plurality of mobile terminals via a channel within a third frequency block.
The present invention, according to a fourth broad aspect, is a mobile terminal arranged to be implemented within a wireless network. The mobile terminal includes an antenna, a transmit apparatus coupled to the antenna and a plurality of receive apparatus that are each coupled to the antenna. The transmit apparatus operates to transmit up-link signals to a Base Transceiver Station (BTS) within the wireless network via a channel within a first frequency block. The plurality of receive apparatus operate to receive down-link signals from the BTS via channels within a plurality of other corresponding frequency blocks.
In a further aspect, the present invention is a Base Transceiver Station (BTS) arranged to be implemented within a wireless network. The BTS including means for receiving up-link signals from a plurality of mobile terminals within the wireless network via a channel within a first frequency block; and means for transmitting down-link signals to a first set of the plurality of mobile terminals via a channel within a second frequency block and transmitting down-link signals to a second set of the plurality of mobile terminals via a channel within a third frequency block.
In yet a further aspect, the present invention is a mobile terminal arranged to be implemented within a wireless network. The mobile terminal including means for transmitting up-link signals to a Base Transceiver Station (BTS) within the wireless network via a channel within a first frequency block; and means for receiving down-link signals from the BTS via channels within a plurality of other corresponding frequency blocks.
The present invention, according to a fifth broad aspect, is a Base Transceiver Station (BTS) arranged to be implemented within a wireless network. The BTS includes one or more antennas, at least one receive apparatus coupled to the one or more antennas and at least one transmit apparatus also coupled to the one or more antennas. The receive apparatus operates to receive up-link signals from a plurality of mobile terminals within the wireless network via a channel within a first frequency block while the transmit apparatus operates to transmit down-link signals to a first set of the plurality of mobile terminals via a channel within a second frequency block. In this aspect, the frequency offset between the channels within the first and second frequency blocks is dynamically controlled.
According to another aspect, the present invention is similar to that of the fifth broad aspect, but is directed to a mobile terminal with an antenna, transmit apparatus and receive apparatus, the transmit and receive apparatus being similar to those within the fifth broad aspect.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.